Net Loss Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 27, 2026	Mar. 28, 2025
Numerator:
Net loss attributable to UCT	$ (17.9)	$ (5.0)
Denominator:
Basic weighted average common shares outstanding (in shares)	45.3	45.1
Effect of potential dilutive securities:
Convertible notes (in shares)	0.0	0.0
Employee stock plans (in shares)	0.0	0.0
Diluted weighted average common shares outstanding (in shares)	45.3	45.1
Net loss per share attributable to UCT:
Basic (in dollars per share)	$ (0.40)	$ (0.11)
Diluted (in dollars per share)	$ (0.40)	$ (0.11)